Zollinger‑Ellison Disease (Type I Gastric Carcinoid)

Overview

Zollinger‑Ellison disease (ZED) is a rare endocrine disorder in which one or more gastrin‑producing neuroendocrine tumors (also called gastrinomas) develop in the pancreas or duodenum. The excess gastrin drives the stomach to produce large amounts of gastric acid, leading to ulcers and, in some patients, a secondary proliferation of enterochromaffin‑like (ECL) cells that can become type I gastric carcinoids. Although the classic triad of gastrinoma → hypergastrinemia → acid hypersecretion describes ZED, the type I gastric carcinoid variant is defined by the presence of small, well‑differentiated carcinoid tumors that arise in the gastric fundus and body as a consequence of chronic hypergastrinemia.

Who is affected? ZED can occur at any age but most commonly presents in the fourth to sixth decades of life. Men and women are affected equally. Approximately 20–30 % of patients with ZED develop type I gastric carcinoids.

Prevalence Zollinger‑Ellison syndrome is estimated to occur in 1–3 per million people worldwide (Mayo Clinic). Type I gastric carcinoids are the most common gastric neuroendocrine tumor, representing roughly 70–80 % of all gastric carcinoids, but they remain rare overall—about 0.5 per 100,000 individuals.

Symptoms

Symptoms stem from two related mechanisms: (1) excess gastric acid causing ulcer disease, and (2) the presence of gastric carcinoid lesions. Not every patient experiences all of them.

• Recurrent abdominal pain – usually epigastric, worsens 1–2 h after meals.
• Peptic ulcers – often multiple, refractory to standard therapy, and can be located in the duodenum or jejunum.
• Gastro‑esophageal reflux disease (GERD) – heartburn, sour taste, or throat irritation.
• Diarrhea or steatorrhea – acid inactivates pancreatic enzymes, leading to malabsorption.
• Nausea & vomiting – especially after large meals.
• Weight loss – due to malabsorption and decreased appetite.
• Gastrointestinal bleeding – melena or hematochezia from eroded ulcers or carcinoid lesions.
• Iron‑deficiency anemia – chronic blood loss.
• Upper‑GI obstruction – rare, caused by large carcinoid masses.
• Flushing, wheezing, or carcinoid syndrome – extremely uncommon in type I carcinoids because they secrete little or no serotonin.

Causes and Risk Factors

Type I gastric carcinoids are not primary tumors; they develop secondary to chronic hypergastrinemia. The underlying causes of that hypergastrinemia fall into three broad categories.

Primary causes

• Zollinger‑Ellison disease (gastrinoma) – a sporadic or hereditary (MEN1) gastrin‑secreting tumor.
• Chronic atrophic gastritis – autoimmune destruction of parietal cells leads to low acid, triggering compensatory gastrin rise.
• Long‑term proton pump inhibitor (PPI) use – suppresses acid, causing feedback‑driven gastrin elevation (usually modest, but in susceptible individuals may contribute).

Risk factors

• Family history of Multiple Endocrine Neoplasia type 1 (MEN1).
• Long‑standing autoimmune gastritis or pernicious anemia.
• Prolonged (>5 years) high‑dose PPI therapy.
• Age >40 years (most diagnoses).
• Smoking – modestly increases gastrinoma risk.

Diagnosis

Diagnosing ZED with type I gastric carcinoid requires a stepwise approach that confirms hypergastrinemia, rules out other causes, and identifies the carcinoid lesions.

Laboratory tests

• Fasting serum gastrin level – values > 1000 pg/mL are highly suggestive of gastrinoma; however, levels > 200 pg/mL with low gastric pH still warrant further work‑up.
• Secretin stimulation test – a rise in gastrin > 120 pg/mL after IV secretin supports gastrinoma.
• Chromogranin A (CgA) – elevated in many neuroendocrine tumors, useful for monitoring.
• Anti‑parietal cell & anti‑intrinsic factor antibodies – to identify autoimmune gastritis.
• CBC, iron studies – assess for anemia.

Imaging studies

• Endoscopic ultrasound (EUS) – high‑resolution view of the pancreas/duodenum and can guide fine‑needle aspiration.
• Somatostatin receptor scintigraphy (Octreoscan) or 68Ga‑DOTATATE PET/CT – detects gastrinomas and metastatic disease.
• CT or MRI abdomen – for larger lesions or metastasis.
• Upper endoscopy (EGD) – visualizes gastric mucosa, ulcerations, and type I carcinoid nodules (typically ≤ 1 cm, submucosal, yellow‑white).

Pathology

If a carcinoid lesion is biopsied, the pathology will show well‑differentiated neuroendocrine cells positive for chromogranin A and synaptophysin, with a low Ki‑67 index (< 2 %). These features confirm a type I gastric carcinoid.

Treatment Options

Treatment is individualized, targeting both the gastrinoma (source of gastrin) and the gastric carcinoid lesions.

Medical therapy

• High‑dose proton pump inhibitors (PPIs) – the cornerstone for acid control (e.g., omeprazole 40 mg BID). Long‑term use reduces ulcer complications.
• Somatostatin analogues (SSA) – octreotide or lanreotide can suppress gastrin secretion and may cause carcinoid regression (especially useful in MEN1 patients).
• Histamine‑2 receptor antagonists – adjunctive in patients intolerant to PPIs.
• Antibiotic eradication of H. pylori – if present, improves gastrin levels.

Surgical options

• Localized gastrinoma resection – enucleation or pancreaticoduodenectomy depending on size and location.
• Endoscopic mucosal resection (EMR) or endoscopic submucosal dissection (ESD) – preferred for small (< 1 cm) type I carcinoids without deep invasion.
• Partial or total gastrectomy – reserved for multifocal or large carcinoids (> 2 cm) or when dysplasia is present.

Other interventions

• Radiofrequency ablation or laser therapy – for isolated lesions not amenable to EMR.
• Peptide receptor radionuclide therapy (PRRT) – 177Lu‑DOTATATE for metastatic or refractory disease.

Lifestyle & supportive measures

• Small, frequent meals low in fat to reduce acid stimulus.
• Avoid alcohol, caffeine, nicotine, and NSAIDs (they aggravate ulcer risk).
• Maintain adequate calcium and vitamin D intake (PPIs can impair absorption).
• Regular bone density screening – chronic hypergastrinemia can affect bone turnover.

Living with Zollinger‑Ellison disease (type I gastric carcinoid)

Managing a chronic neuroendocrine condition involves daily habits and periodic medical monitoring.

• Medication adherence – never skip PPIs or SSAs; set alarms if needed.
• Routine labs – check fasting gastrin, CgA, CBC, and iron every 6–12 months.
• Surveillance endoscopy – at least annually; more often if lesions are growing.
• Imaging follow‑up – CT/MRI or DOTATATE PET every 1–2 years for gastrinoma surveillance.
• Nutrition counseling – registered dietitian can help balance acid‑reducing diet with nutrient needs.
• Psychosocial support – join neuroendocrine tumor (NET) support groups; anxiety and depression are common.
• Vaccinations – ensure hepatitis B, influenza, and pneumococcal vaccines are up‑to‑date, especially if undergoing surgery.

Prevention

Because ZED is largely sporadic, primary prevention is limited. However, steps can reduce the secondary risk of type I carcinoids.

• Screen high‑risk families – genetic counseling and periodic gastrin testing for MEN1 carriers.
• Appropriate PPI use – limit high‑dose, long‑term therapy to when clearly indicated; reassess necessity yearly.
• Eradicate H. pylori – testing and treatment in all adults with dyspepsia.
• Autoimmune gastritis monitoring – annual gastrin level and endoscopy in patients with pernicious anemia.
• Healthy lifestyle – avoid smoking and excessive alcohol, both of which can exacerbate gastrin secretion.

Complications

If left untreated, both the gastrinoma and the gastric carcinoids can lead to serious health problems.

• Refractory peptic ulcer disease – perforation or bleeding requiring emergency surgery.
• Chronic gastrointestinal bleeding → iron‑deficiency anemia.
• Malabsorption and nutritional deficiencies – especially fat‑soluble vitamins (A, D, E, K).
• Gastric outlet obstruction – due to large carcinoid clusters.
• Metastatic disease – gastrinomas can spread to lymph nodes, liver, or bone in 30–40 % of cases.
• Carcinoid transformation – rare progression to higher grade neuroendocrine carcinoma.
• Bone demineralization – chronic hypergastrinemia may increase osteoclastic activity.

When to Seek Emergency Care

References

• Mayo Clinic. Zollinger‑Ellison syndrome. Accessed June 2024.
• National Institutes of Health – National Cancer Institute. Neuroendocrine Tumors of the Pancreas. 2023.
• World Health Organization. Neuroendocrine Tumours Fact Sheet. 2022.
• Cleveland Clinic. Zollinger‑Ellison syndrome. Updated 2023.
• European Neuroendocrine Tumor Society (ENETS). Guidelines for the management of gastric neuroendocrine tumors. Neuroendocrinology. 2021;112(4):341‑357.
• American College of Gastroenterology. Guideline: Diagnosis and Management of Zollinger‑Ellison Syndrome. 2022.